Draco (constellation)
- Little Dipper
- Giraffe
- Big Dipper
- Bootes
- Hercules
- Lyre
- Swan
- Cepheus
The Dragon ( Draco in Latin ) is a constellation of the northern sky. It is circumpolar for Central Europe, that is, on visible in our latitudes throughout the year.
Description
The dragon is a very vast constellation that stands out as a long star train to the Little Bear (Ursa Minor) around winds. The head is formed by four stars, the - are directed to Hercules - according to the mythology. He stares at this with two different colored eyes, the stars β ( Alwaid, yellow-green ) and γ ( etamin, red).
At the head of the dragon, near the Cat's Eye Nebula, is the north pole of the ecliptic to the celestial north pole of the (extended axis of the earth ) moves once around due to the precession in 25,800 years.
History
The dragon is one of the classic 48 constellations of the ancient world, mentioned by Ptolemy.
In the ancient Greek astronomy the Little Bear was part of the dragon whose wings he made.
Due to the precession of the earth Thuban was the pole star of the northern sky 5,000 years ago. The least distance to the exact celestial pole was reached at 2830 BC with 10 minutes of arc.
Mythology
To the mythological origin of the constellation are several versions:
So shall the dragon represent the monster that was killed by Cadmus before founding the city of Thebes.
In the Argonauts led by Jason the dragon guarded the Golden Fleece.
In the sagas surrounding Heracles it was Ladon, a hundred -headed dragon. Heracles was given the task to steal the golden apples of the Hesperides, whose enjoyment of immortality and eternal youth promised. The apples were strictly guarded by Ladon and the Hesperides. Heracles was finally able to take the apples.
To this end, there are again two versions:
For one, he is said to have persuaded the Titans Atlas to fetch the apples for him while he took off his heavy burden to carry the heavens. The other version after Heracles took the apples himself, where he killed the dragon. Heracles was also immortalized as a constellation. It is located under the Roman name Hercules near the dragon's head in the sky.
Celestial objects
Stars
The names of the stars Ettanin, Thuban and Rastaben are Arabic in origin and are derived from the Arabic name given to Dragon from.
Ettanin, the brightest, is 150 light years distant star of spectral type K5 III.
Double stars
ν Draconis is a binary star system in 120 light years away. The two components can already be resolved with a prism binoculars in single stars due to the wide angular distance of nearly 62 arc seconds.
39 Draconis is a 150 light-years distant multiple star system in which three stars orbit a common center of gravity.
Variable Stars
The stars R and T Draconis are pulsationsveränderliche Mira -type stars. It involves luminous red giants or supergiants, which expand and contract rhythmically again, which can be observed as significant brightness variation. While the maximum of R and T are so bright that they can be tracked with binoculars. At a minimum, their brightness drops below 13m, so that their observation requires a larger telescope.
Messier and NGC objects
NGC 6543 is a planetary nebula, which is a star that has shed the outer shell of gas at the end of its development. In the center is an extremely hot white dwarf star. NGC 6543 appears in the telescope as a diffuse nebula with a faint star in the center. The complex structure of the nebula, which gave him the name Cat's Eye Nebula is visible only on long-exposure photographs. The Hubble Telescope yielded particularly impressive images of the nebula.
The Messier object M102 is a spiral galaxy of type S0 to 30 million light years away.
NGC 5907 and NGC 6503 are spiral galaxies of type Sc in 30 or 15 million light -years away.
All three galaxies are in the telescope is not very noticeable and appear as misty spot.